Peace is naturally within everyone, but because of the way a person is conditioned the mind is in a constant state of some activity and this is why one’s natural state of peace isn’t noticed.
Thinking is an activity of the mind and regardless of what the thoughts are, it takes one from the minds place of non activity and thus peace. There’s nothing that can be done to prevent this from happening, but one can become aware of it; the reason nothing can be done is because anything that’s done becomes a mind activity. Notice when the mind is in a state of peace and what takes you from this state. There are so many activities of the mind that takes away one’s peace that the list is endless, but it wouldn’t matter if there was only one activity on the list, as long as one is in unaware of the activity it will take you from your place of peace.
To notice this activity is a very simple practice, just watch the activity, nothing more. I’m sure you’ll be amazed at how much activity and how little non activity there is. Watch when an itch arises and how the mind activity now becomes to scratch the itch. Can you notice this and not scratch? This is something simple to start with and when you become aware of this you can watch other mind activities as they arise. The key is not to say to yourself “I’m not going to scratch” it’s to just be with the itch and watch it. Most times the itch will simply go away. This is how it is with most mind activities, but it will take some practice (just watching) for the awareness of this to take hold because of the conditioned thinking that’s in place. Just watch the conditioned mind activity, don’t do anything but watch it, thought in, thought out, thought in, thought out, and ever so slowly the activity will lessen and in the process there will be more peace (naturally). Simple yes, but don’t make it something that needs to be done or it will just become another conditioned mind activity.